The invention relates to a rotatable high-current connector for feeding electrical lines through to movable elements in closed spaces such as a vacuum chamber includes a coaxial arrangement of an inner current carrying tube and an outer current carrying tube insulated from each other. Each tube has a metal flange connected to a corresponding concentrically situated counter flange by flexible current bridges to permit rotation between the flanges and the counter flanges.
High-current connectors of the above-described kind are needed, for example, of the input of heavy working currents into closed spaces whenever limited rotating and turning movements have to be performed between components inside and outside of the walls of these spaces. This need consists, for example, in the case of electrically powered apparatus, especially those supplied at medium frequency, such as melting and casting apparatus in which the molten material is cast by the tipping of a crucible, wherein the heating means forms one unit with the crucible.
It is especially important in this case that the high-current connector serve simultaneously also for the entry and exit of a coolant by which furnace parts, such as an induction coil, are protected against overheating.
In apparatus where there are pressure differences on both sides of the walls of the closed chambers, as for example in vacuum furnaces, the sealing of the high-current connectors has to satisfy special requirements. High-current connectors of the kind described above, however, are not limited to use in melting and casting furnaces.
A high-current connector of the kind described above has been the prior art for many years due to public usage. It consists of four metal annular flanges which are arranged concentrically one inside the other in paris and joined together by loops of stranded wire so that one inner and one outer flange are at the same potential. The annular flanges of different polarity arranged back-to-back are insulated electrically from one another by spacer rings, but mechanically they form one unit, the inner annular flanges being able to perform a limited turing movement against the outer annular flanges. The stranded wires are in this case fastened at their ends in the flanges by means of set screws, for example. The strands of wire of the one potential are approximately in mirror-image symmetry with those of the other potential, the plane of symmetry being approximately inside of the insulating spacer rings between the flanges. The angle of movement is provided for by making the looped length of the stranded wires sufficiently great. The inner, rotatable annular flanges have different diameters and are situated on the outer surfaces of the coaxial tubes which carry the current and the coolant through the wall of the closed chamber to the movable components therein.
The supply of electric current to the outer, stationary counter-flange is accomplished in accordance with German Patent 32 19 721 (U.S. Pat. No. 4,492,423) by means of two tangentially disposed tubular conductors which are configured simultaneously as coolant lines.
In a configuration of the above-described kind, however, the disadvantage has been encountered that the transfer of high electric currents is problematical. The introduction of the electric current into the counter-flange takes place at only one radially external point. Since the electric current tends to flow along the shortest possible path, no distribution to the annular counter-flange takes place. Instead, the current flows through the stranded wires situated close to the conductor into the counter-flange. This in turn causes different thermal loading of the stranded wires, and for this reason they are made with different diameters.